<nav class="navbar">
    <div class="container">
        <div class="navbar-header">
            <a class="navbar-brand" href="#">天一总局</a>
        </div>
        <div id="navbar" class="navbar-collapse collapse">
            <ul class="nav navbar-nav">
                <li><a href="#">首页</a></li>
                <li><a href="#">最新动态</a></li>
                <li><a href="#about">美图欣赏</a></li>
                <li><a href="#contact">话说历史</a></li>
                <li class="dropdown">
                    <a href="#aaa" class="dropdown-toggle" data-toggle="dropdown" role="button"
                    >关于我们 <span class="caret"></span></a>
                    <ul class="dropdown-menu">
                        <li><a href="#">Action</a></li>
                        <li><a href="#">Another action</a></li>
                        <li><a href="#">Something else here</a></li>
                        <li role="separator" class="divider"></li>
                        <li class="dropdown-header">Nav header</li>
                        <li><a href="#">Separated link</a></li>
                        <li><a href="#">One more separated link</a></li>
                    </ul>
                </li>
            </ul>
        </div>
    </div>
</nav>